This is a no brainer for me, N64.
Super Mario 64 is one of my favourite games of all time and the N64 had some really great games that I loved playing back in the day... maybe not so good now, but hey, the nostalgia is strong!
A few "lesser" games I loved;
- Mischief Makers
- Quest 64 (Shut up, it's good!)
- Mystical Ninja
- Blast Corps
- Body Harvest
... Lesser in the sense that not enough people talk about them, I loved them all! :P